The increasing globalization of the agrarian markets necessitates an increasing degree of rationalization also in agricultural enterprises. Milk producing enterprises use therefore almost exclusively automatic milking plants. Hence, these plants have, on the one hand, the function of markedly increasing the milking capacity, i.e. they should be able to milk more animals per unit time, so as to increase the productivity of the agricultural enterprise, and, on the other hand, the physical and also the psychical strain to which the animals are subjected by the mechanical milking process should be reduced to a minimum by these plants.
An ideal milking plant should therefore be capable of processing during the milking operation a big flow of milk adapted to the standard of today's top cows, and, in so doing, it should simulate the natural sucking of a calf on its mother's udder. Only a milking process which simulates natural sucking will guarantee a complete evacuation of the udder and therefore a high yield of milk, the health of the teat and of the udder as well as mental well-being of the animal, which will also result in higher yields of milk in the long run. Any kind of treatment and any device which may cause the animal to feel uncomfortable should be avoided during the milking process. In particular the area of the milking plant which is in contact with the animal's teats directly or indirectly should be implemented such that the animal is not subjected to any irritation at all.
In the nowadays almost exclusively used milking plants the milk is extracted from the teat during the suction phase by means of a teat cup lined with a soft teat rubber. During this suction phase the teat cup dings to the teat only due to the operational vacuum prevailing in the plant. The extracted milk then flows through a connection hose, the so-called short milk hose, into a multiway valve, and from this multiway valve it is advanced into different line systems or collecting receptacles. During a second phase, the so-called relief phase, air at atmospheric pressure is introduced into the space between the teat rubber and the teat cup via a thin flexible hose so that the teat rubber will contract due to the negative pressure prevailing therein and interrupt the flow of milk from the teat to the outlet of the teat cup. In this phase, part of the teat rubber clings softly to the teat and the adherence of the teat cup to the teat is increased by the friction occurring between the teat and the teat rubber in addition to the still existing vacuum.
The change over from the suction phase to the relief phase takes place approx. 60 times per minute and leads to light shocks or vibrations due to the pressure fluctuations occurring during the change from one phase to the other and due to the change in the conditions under which the teat cup adheres to the teat. Due to the varying conditions under which the teat cup adheres to the teat, it is in Germany normally common practice to operate the milking plant in an alternating two-phase mode, i.e. two teat cups are in the suction phase, whereas the other two are in the relief phase.
The teat cups are mechanically coupled to the multiway valve essentially via the four short milk hoses and, consequently, they are also mechanically coupled to one another. Since the short milk hoses have to transfer the flow of milk as well as the operating vacuum, an interior diameter of approx. 9-11 mm proved to be advantageous in existing plants. In addition, the ordinance concerning milk production demands that foreign matter originating from lines or receptacles must not be transferred into the milk. Since the milk hoses are produced from plastic material so as to guarantee the highest possible flexibility, the requirements on a high mechanical stability on the one hand (the interior diameter of the milk hose must not undergo any substantial deformations at a negative pressure of approx. 0.5-0.7 bar so as to avoid a negative influence on the flow velocity of the flow of milk) and the chemical passivity of the hose material on the other hand (the use of certain additives causing a stability of the material in the case of small wall thicknesses is not allowed) lead to embodiments of the milk hose having a comparatively large wall thickness. This has the consequence that the originally desired flexibility of the short milk hoses is markedly restricted. Hence, a comparatively strong mechanical coupling exists between the four teat cups via the milk hoses and via the multiway valve, and this has the effect that a change in the external conditions at one teat will also affect all the other teat cups. The comparatively rigid connection between the individual teat cups has e.g. the effect that, due to the different degrees of evacuation of the udder quarters during the milking process, in the course of which one teat cup gradually moves upwards (“climbs”) until the edge of its opening is stopped by the udder, the other teat cups will be affected as well. This leads to tensions at the udder and therefore to an irritation of the animal and it may cause a premature interruption of the flow of milk in the case of the udder quarters which have not yet been emptied.
In addition, the constant twisting and bending forces acting on the short milk hoses entail a high degree of wear of the short milk hoses and a resultant fracture of the material, in particular at the transition points to the connection necks leading to the teat cups and the directional valve, respectively.
It is therefore the object of the present invention to provide short milk hoses which fulfill the requirements mentioned at the beginning more effectively than the conventional milk hoses used.
According to the present invention this object is achieved in that a flexible milk hose is provided, which is characterized in that it comprises a centre piece having a higher flexibility than the two end portions, said higher flexibility increasing towards the middle of the centre piece.
The structural design of the centre piece of the milk hose permits, on the basis of the increase in elasticity in a defined area (centre piece) of the milk hose, an absorption of twisting and bending forces by elastic deformation, the end portions, especially the transitions to the connecting necks, having hardly any load applied thereto. This effect is supported especially by the flexibility of the milk hose which increases towards the centre, since the radius of curvature of the milk hose is larger in the vicinity of the end portions than in the area of the centre of the hose and since, consequently, the mechanical load applied to the end portions is not as large.
In accordance with an advantageous embodiment, the centre piece comprises spaced-apart reinforcement elements enclosing, at least partially, the circumference of a certain area of the centre piece. This kind of structure permits a wall thickness which is fundamentally smaller than the wall thickness that could be used for a milk hose having no reinforcement elements. The areas between the reinforcement elements have therefore a high elasticity, the stability vis-a-vis the pressure difference being guaranteed by the reinforcement elements. It will be suitable when the reinforcement elements consist, at least partially, of a material whose elasticity is lower than that of the material which has been used for producing an area between said spaced-apart reinforcement elements. A big difference in the elasticities of successive areas permits the creation of reinforcement elements having e.g. a high dimensional stability so that a larger distance can be used, and this will, in turn, lead to a higher elasticity of the intermediate space (material of high elasticity) and therefore of the whole centre piece.
In accordance with a further preferred embodiment, the reinforcement elements contain a metal or a plastic material whose hardness is greater than that of the hose. Minimum dimensions in combination with high strength can be achieved, when e.g. rings or clips consisting of metal or of a hard plastic material are integrated in the hose wall of the centre piece.
In accordance with a further advantageous embodiment, the distance between the reinforcement elements decreases from the middle of the centre piece towards the respective first and second end portions. By means of this arrangement a decrease in the flexibility of the milk hose from the middle towards the outside is achieved, whereby it is guaranteed that a curvature of the element will occur substantially in the middle of the hose.
According to a further preferred embodiment, the reinforcement elements are implemented as spaced-apart elevations enclosing the circumference of the centre piece at least partially. This structure of the reinforcement elements has the advantage that the reinforcement elements may perhaps be applied subsequently to a suitably shaped milk hose.
In accordance with an advantageous embodiment, the wall thickness in an elevation exceeds the wall thickness in an area in which no spaced-apart elevations exist. Due to the increased amount of material provided in the area of an elevation, the necessary mechanical stability vis-a-vis the pressure differences occurring is guaranteed, even if the effective wall thickness of the areas between two elevations on the outer edge of the curvature of the hose will be reduced when the centre piece is being bent. Hence, it is possible to produce the centre piece from a uniform material.
According to another preferred embodiment, the whole flexible milk hose is produced from a uniform material. The milk hoses can therefore be produced at a moderate price.
In accordance with a further advantageous embodiment of the present invention, the elevations and the areas between two respective neighbouring, spaced-apart elevations have substantially the same wall thickness. Due to this structural design, which is similar to that of a bellows, the milk hose is particularly flexible and it is especially also adapted to be stretched and compressed, respectively, in the longitudinal direction. By enlarging the wall thickness in this area, it is possible to achieve by means of said increased wall thickness, in spite of the bellows-like structural design, a good stability against deformations of the interior diameter caused by pressure fluctuations and to maintain simultaneously a high flexibility, especially in the longitudinal direction. In addition, this embodiment is particularly suitable for imitating the natural sucking of the calf on the teat of the brood animal on the basis of the compression and stretching taking place in the longitudinal direction of the centre piece of the flexible milk hose during the change-over from the suction phase to the relief phase. On the basis of this alternating stretching and compression of the milk hose, the pendulum motion of the milking unit produced by the pressure differences occurring during the change-over from one phase to the other will be intensified and the teats will additionally be stimulated and the muscles of the udder relaxed in the rhythm of the phase change, similar to the effect produced when a calf is sucking on the udder.
In accordance with a further preferred embodiment, the first and second end portions have each formed thereon a reinforcement element. This measure serves to achieve a higher bending stiffness especially in the connection area of the milk hose, whereby bending will substantially occur in the centre piece, as intended, when a mechanical load is applied to the milk hose. This will reduce the risk of tearing of the hose, especially at the transition from the connecting neck to the connection element.
It will be advantageous when the wall thickness of the reinforcement elements exceeds that of the residual area of the first and second end portions. It is thus possible to stiffen the end portions, even if the milk hose is produced from one uniform material.
In accordance with another preferred embodiment, the interior diameter of the centre piece does not vary in this area. In the case of this embodiment, the flow of the stream of milk will not be impaired by interaction with the inner surface, e.g. by the formation of vortices on indentations on said surface. Furthermore, the fluid connection element can be cleaned easily.
According to another preferred embodiment, the wall thickness of the centre piece decreases from the first and second end portion towards the middle of said centre piece.
This permits the milk hose to be produced in a simple way, since the outer surface can be implemented as a smooth surface. The minimum wall thickness in the central area is chosen such that a sufficient dimensional stability of the milk hose under vacuum is still guaranteed. The wall thickness of the centre piece preferably decreases continuously towards the middle. It is, however, also possible to provide a step-like profile of the wall thickness; in this case, the axial dimensions of each of the respective areas of different wall thicknesses can be identical or different.
In accordance with a further preferred embodiment, the wall thickness of the reinforcement elements is smaller in the area of the middle of the centre piece than the wall thickness of the reinforcement elements arranged in the boundary area of said centre piece.
According to another preferred embodiment the wall thickness of the reinforcement elements decreases continuously towards the middle of the centre piece.
In accordance with a further preferred embodiment, the wall thickness of the intermediate areas between two neighbouring reinforcement elements is smaller in the area of the middle of the centre piece than the wall thickness of the intermediate areas of the reinforcement elements arranged in the boundary area of said centre piece.
According to another preferred embodiment, the wall thickness of the intermediate areas decreases continuously towards the middle of said centre piece.
The present invention will now be explained and described in detail making reference to embodiments and the drawing enclosed, which refer to these embodiments and in which: